Methods of stereology will be applied to electron micrographs to obtain volume estimates for cells, mitochondria and tonofilament bundles. The frequency of desmosomes and hemidesmosomes will be determined. The material to be examined comprises biopsies of 11 orthokeratinized leukoplakias in different oral regions and control regions from the same patients. Three control biopsies are from orthokeratinized regions, and eight are the normal counterparts of the leukoplakic regions. Estimates will be made at three epithelial levels.